The subject invention relates to a process for making tubular glass fiber pipe insulation and more specifically, to an improved process for making tubular glass fiber pipe insulation that is made from a glass fiber mat produced utilizing a rotary glass fiberization process wherein the mat, when pulled apart by longitudinally directed, opposing forces, separates across the width of the mat into two mat sections having feathered edges with substantially no fibrous stringers extending beyond the feathered edges of the mat a distance greater than about four inches and typically no fibrous stringers extending beyond the feather edges of the mat a distance greater than about three inches.
Tubular glass fiber pipe insulation is typically made from a glass fiber mat containing uncured binder by winding the glass fiber mat about a mandrel and curing the binder. The glass fiber mat is typically made utilizing a process known in the industry as a pot and marble fiberization process or a process known in the industry as a rotary fiberization process. The glass fiber mat utilized from either of these processes typically contains fibers ranging between 5 and 8 microns in diameter rather than the finer diameter fibers normally used in products such as residential building insulation. The larger diameter glass fibers utilized in the glass fiber mats to produce tubular pipe insulation, at least in part, provide the finished tubular pipe insulation product with the feel expected and the rigidity required of the product by the insulation contractors. However, when making a glass fiber mat containing fibers ranging between 5 and 8 microns for forming tubular pipe insulation with a rotary fiberization process, a number of processing problems are encountered as illustrated by the following examples.
For the weight range of the mats that are used to make tubular pipe insulation and the downstream speed limitations of pipe insulation production processes, the pull rate per rotary fiberizer used to make the relatively large diameter glass fibers in the quantities required to be collected into such mats is relatively low when compared to the pull rates normally encountered in commercial rotary glass fiberization processes and can increase the difficulty of maintaining the energy balance required by the process to produce such glass fibers. The elevated glass viscosity of the molten glass used to make glass fibers for pipe insulation, compared to the glass viscosities typically used in other commercial rotary glass fiberization processes, increases the energy required to centrifuge the molten glass into fibers and limits the molten glass throughput through conventionally sized spinner fiberization holes. Furthermore, spinner alloy service temperature limitations inhibit raising the operating temperatures of the process as a means to compensate for and reduce this elevated viscosity.
Another issue that must be overcome when utilizing a rotary fiberization process is the networking of the glass fibers where the glass fibers produced by the process become entangled together prior to their collection into a mat to the extent that the process and mat produced by the process are adversely affected by the networked glass fibers. The accumulation of the glass fibers produced in the process into large networks of glass fibers can adversely affect the application of binder to the glass fibers and the collection of the glass fibers into a mat having a generally uniform fiber weight distribution and tear strength. When a mat containing networks of glass fibers that are too large is pulled apart during the process to separate the mat into mat sections that are successively wound about mandrels to form tubular pipe insulation, the networked glass fibers can adversely affect the uniform tearing of the mat so that the mat sections formed do not have generally straight feathered leading and trailing mat section edges and can form fibrous stringers extending beyond the leading and trailing edges of the mat sections for distances that create processing and/or finished product problems. For example, the presence of these stringers can adversely affect the winding the mat sections about the mandrels to form a tubular pipe insulation product through their entanglement with the winding apparatus and can adversely affect the appearance of the outer surface of the finished tubular pipe insulation product by making the outer surface of the product irregular. Furthermore, where the separated mat sections have relatively thick and/or ragged leading and trailing edges rather than generally straight feathered edges, the spiral winding of a mat section onto a mandrel to form a tubular pipe insulation product can leave a longitudinally extending ridge on the internal surface of the product that adversely affects the product's insulating properties and/or a longitudinally extending ridge on the external surface of the product that adversely affects the product's appearance.